The invention relates to a plant for producing wood pellets or other solid granules from small pieces of material of organic and/or plant origin suitable for being automatically fed to energy generating plants or other consumers, comprising devices for adding, preparing, drying, pressing, cooling and discharging the material that are at least partially arranged in individual transportable containers that can be assembled like modules for least part of the plant.
Wood pellets are rod-shaped granules that consist of sawing or planing shavings, wood chips, wood shredder material or other byproducts, or waste from the timber and forest industry. Other solid granules consisting of small pieces of material of organic and/or plant origin can for example be produced from straw, sunflower seed shells, olive pits and olive pressing residue, rice husks and other biological residue from, for example, agriculture and the food industry.
In the production of wood pellets, the supplied material is prepared to be pelletized, for example by commutation, drying and conditioning. The pellets are pressed from the prepared material. For this, an edge runner press is used in which the material is pressed through a die with holes according to the desired pellet diameter. The lignin contained in the material is released by the heating during conditioning, or respectively during the pressing process, and bonds the individual wood particles to each other. In addition to the lignin present in the wood, additional binding agent can be used. A knife cuts the pellet strands to the desired length after leaving the die. Then the pellets are cooled and thereby solidified.
Plants for producing wood pellets or other solid granules from small pieces of material of organic or plant origin are generally planned and developed by engineering offices or plant builders as individual projects for specific locations. In the process, machines and assemblies from different manufacturers are integrated, and interfaces and the transfer of material are worked out on a case-by-case basis depending on the respective situation. This frequently requires adaptations and improvements during assembly and elevated operating costs while operating the system.
The disadvantage of conventional pelletizing plants is high investment costs since basic engineering, detailed planning and architectural services must be performed on the setup site. This increases the cost risk since individual orders are involved (sometimes one-off production). Furthermore, there are problems with interfaces between different trades which necessitates adaptations. In each plant, safe operational management must be established by optimizing the processes. Since these are individually planned plants, the expense for stocking spare parts is high. Managing projects on-site requires a long planning and preparation phase. In addition, there are long assembly times and uncertain startup times.
EP 1 849 851 A2 describes a device for producing wood pellets from comminuted wood material which is purportedly easy and economical to set up and subsequently operate, and is also transportable. It is easily adaptable to new requirements such as changed processing quantities. For this purpose, the device has a frame scaffold with support panels or support racks for attaching hoppers, presses, coolers and dedusting devices. Cover panels can be attached to the frame scaffold. The frame scaffold and the plant parts attachable thereto constitute a transportable production module with a predetermined throughput. As needed, a plurality of these production modules can be combined in order to thereby increase the throughput without changing the dimensions of the plant parts of a production module. A disadvantage is the major effort in transporting the entire plant in one piece, and adapting to needs by combining a plurality of complete production modules.
DE 10 2006 061 340 B3 describes a facility for producing wood pellets with at least one assembly module for adding, drying, pressing and discharging. The assembly modules are introduced in a vertical arrangement of the respective functional assemblies in internationally standard containers (12 or 20 foot containers) A plurality of containers forming a horizontal and/or vertical row are connected to each other by electrical and/or pneumatic media lines, and one of the containers is connectable to a locally available media source. The easy and quick assembly of the plant is advantageous which consists of prepared assembly modules. The plant can be easily moved to a different location and only has to be locally stationary for a time. The disadvantage is that a drying shaft extends vertically over a plurality of stacked containers that are separated from each other during transport and must be joined together at the site of use. Another disadvantage is the limited output of the counter air cooler and the major energy requirement for the aspiration and separation of the wood dust. This comprises a container that can be filled from above with pellets and through which cooling air can flow from below, and from which the pellets are released at the bottom after cooling. Another disadvantage is the spatial allocation and proposed setup of the assembly modules that significantly increase the risk of damage in the event of fires and render extinguishing difficult. The high energy use, in particular for heating the raw material in the curing container by supplying extra generated energy is also disadvantageous.
Against this background, an object of the invention is to create a plant for producing wood pellets or other solid granules that can be transported, set up and move to a different location with less effort, and that enables energy-optimized operation.